The invention relates to an apparatus for generating acoustic shock waves with a single shock wave tube and for focusing them onto a focus region. The invention particularly relates to the fragmentation of concrements (e.g. kidney stones) in a living being.
Shock wave tubes for generating acoustic shock waves are known. As indicated in German Offenlegungsschrift No. 33 12 014, shock wave tubes can be employed for the fragmentation of concrements in the body of a patient. This publication discloses a shock wave tube whose coil is curved, so that the emitted shock wave converges in a focus. In front of the coil, an insulating foil and a metal diaphragm are arranged. A voltage pulse is applied to the coil by means of a capacitor, and as a result the metal diaphragm is repelled from the coil. In this way the shock wave treatment is generated.
A shock-wave tube of the type considered herein is also described in commonly owned patent application Ser. No. 634,021, filed 07/24/1984 and entitled "Apparatus for the Contact-Free Desintegration of Calculi", the disclosure of which application is incorporated herein by reference.
Before the next shock wave is triggered, the capacitor must be recharged, which requires time.
For the fragmentation of, e.g. kidney stone in a adult person, a plurality (e.g. 500) of such shock waves (and hence a corresponding treatment time) is necessary. The effect of the shock waves can be improved if they are so closely spaced in time that they overlap in their action on the concrement. It has been proposed to provide several shock wave tubes in parallel and to activate them at short intervals in sequence. This procedure is relatively costly, because essential parts of the arrangement, such as the capacitor, spark gag and the shock wave tube itself, must be multiplied.
One object of the present invention is to develop an apparatus in which despite the existence of only one shock wave tube, time-staggered shock waves can be directed to the concrement.